AVIATION FORECAST DISCUSSION FOR 00Z TAF CYCLE
AFDCHI LITTLE TO ADD TO PUBLIC DISCUSSION BELOW. JUST A FEW CIRRUS UNTIL
MID MORNING OR SO FRIDAY...THEN LOWERING CIGS. WINDS TO SLACK OFF
TONIGHT...THEN PICK UP FROM EAST AND NORTHEAST BEGINNING JUST BEFORE
DAYBREAK...INCREASING DURING THE DAY.
JHV
PUBLIC DISCUSSION FOR 330 PM GRIDS/ZONES:
MAIN FORECAST CONCERNS CONTINUE TO REVOLVE AROUND WINTER STORM
SYSTEM SHAPING UP FOR FRIDAY THROUGH FRIDAY NIGHT. THINKING HAS NOT
CHANGED MUCH FROM PREVIOUS DISCUSSION/UPDATES...THOUGH BRIEF LOOK AT
NEW 18Z MESO-ETA SHOWS A SLOWER ARRIVAL OF PRECIP FRIDAY. EXPECT
SIGNIFICANT FREEZING RAIN/ICING PROBLEMS ACROSS FAR SOUTHERN REACHES
OF THE FORECAST AREA...AS THERMAL ADVECTION RESULTS IN WARM LAYER
ALOFT ON THE ORDER OF +4 DEGREES FROM 12Z FORECAST SOUNDINGS...WHILE
SURFACE BASED LAYER REMAINS BELOW OR JUST AT FREEZING. MORE
DIFFICULT QUESTION IS WHAT HAPPENS FARTHER NORTH...WHERE PRECIP
EXPECTED TO BE ALL SNOW. 3-4 G/KG AVAILABLE ON 295K SURFACE...THOUGH
ISENTROPIC LIFT DECREASES RAPIDLY TO THE NORTH TOWARD WI BORDER.
FRONTOGENETIC FORCING IS IMPRESSIVE IN 850-500 MB LAYER...BUT WITH
DRY NORTHEAST LOW LEVEL FLOW EXPECT RAPID CUT OFF TO NORTH SIDE OF
PRECIP SHIELD. THUS NARROW STRIPE OF HEAVY SNOW POSSIBLE...WITH
AMOUNTS THEN TRAILING OFF RAPIDLY TO THE NORTH. EXACTLY WHERE THAT
BAND WILL BE CENTERED IS THE TOUGH QUESTION...BUT THINK AT THIS TIME
THAT THE AREA FROM ROCHELLE TO THE SOUTH HALF OF THE CHICAGO METRO
AREA AT GREATEST RISK FOR POTENTIAL 6" SNOW AMOUNTS WHEN ALL IS SAID
AND DONE. GARCIA METHOD WITH 3-4 G/KG SUGGESTS 6 TO 8 INCH POTENTIAL
MAX...THOUGH AGAIN THIS MAY BE LIMITED TO VERY NARROW AREA. BASED ON
CONTINUED UNCERTAINTY...AND WITH PRECIP NOT EXPECTED UNTIL SECOND
PERIOD...WILL CONTINUE WITH WINTER STORM WATCH AT THIS TIME AND
ALLOW ADDITIONAL DATA FROM 00Z RUNS TO BE ANALYZED BY EVE OR MID
SHIFT FOR POSSIBLE UPGRADE TO ANY WRNGS/ADVSRYS.
FORECAST SOUNDINGS SUGGEST FZRA/PL SHOULD CHANGE TO SNOW ACROSS
SOUTHERN SECTIONS FRIDAY EVENING/NIGHT...WITH SNOW DIMINISHING NORTH.
DIFFERENCES IN AVN/ETA DEPICTION OF EVENTS SATURDAY...WITH ETA
PULLING SYSTEM OFF TO THE EAST AS WEAK MID LEVEL TROUGH
PASSES...WHILE AVN CONTINUES TO DEVELOP SIGNIFICANT PRECIP ALONG
BAROCLINIC ZONE. HAVE CHOSEN A COMPROMISE HERE IN ENDING OF PRECIP
BETWEEN THE TWO...KEEPING CHANCE SNOW NORTH AND LIKELY SOUTH BEFORE
ENDING ALL AREAS BY SUNDAY MORNING.
COORD WITH...MKX...IND...ILX...DVN.
.CHI...WINTER STORM WATCH FRIDAY THROUGH EARLY SATURDAY.
RATZER
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
AFDDDC 315 PM CST THU FEB 13 2003
DAYS 1-2...
QUESTIONS THIS CYCLE ARE TEMPERATURES AND TIMING AND TYPE OF
PRECIPITATION.
THE 12Z DIAGNOSTICS SHOW THE SOUTHERN BRANCH SYSTEM EJECTING INTO
THE CENTRAL AND SOUTHERN PLAINS ON A 130-140KT JET STREAK ACROSS
MEXICO INTO NEW MEXICO. THIS FLOW IS CONTINUING THE TROPICAL
MOISTURE FETCH ALOFT INTO THE SYSTEM WHILE THE OPEN GULF OF MEXICO
IS NOW ALLOWING PLENTY OF LOW LEVEL MOISTURE TO STREAM NORTHWARD
INTO SOUTHWEST OKLAHOMA HEADING FOR KANSAS. A SURFACE LOW CONTINUES
TO DEEPEN IN NORTHEAST NEW MEXICO AND SOUTHEAST COLORADO IN RESPONSE
TO THE MID TROPOSPHERIC SHORT WAVE TROUGH MOVING THROUGH. WIDESPREAD
PRECIPITATION IN ISENTROPIC LIFT HAS NOW BROKEN OUT ACROSS THE
FORECAST AREA AS ANTICIPATED YESTERDAY. THE NORTHERN BRANCH POLAR
FRONT REMAINS DRAPED ACROSS THE CENTRAL CONUS FROM WYOMING TO
ARKANSAS WITH THE COLDER AIR NORTH OF IT POISED TO BECOME INVOLVED
WITH THE STORM AS THE SURFACE LOW DEEPENS AND MOVES EASTWARD TONIGHT
INTO FRIDAY.
MODEL INITIALIZATIONS PROBABLY SUFFERED DUE TO THE LACK OF MEXICAN
UPPER AIR DATA AGAIN TODAY. AM UNSURE WHAT THE PROBLEM IS, BUT THE
MEXICAN SOUNDINGS HAVE BEEN CONSPICUOUS BY THEIR ABSENCE FOR SOME
TIME NOW. FORTUNATELY THERE WERE AT LEAST SOME AIREPS AND ACARS
ACROSS MEXICO THIS MORNING WHICH WILL HELP WITH THE UPPER LEVEL MASS
FIELDS BUT WILL DO LITTLE FOR THE THERMODYNAMIC PROFILES. BY 18Z IT
HAD BECOME CLEAR THAT THE ETA WAS CONTINUING ITS RECENT BIAS OF
BEING FAR TO DRY AND A LITTLE TOO WARM. WILL AGAIN USE THE MORE
REALISTIC GFS TODAY AS IT HAS NICELY CAPTURED THE PRECIPITATION AND
LOW LEVEL MOISTURE MISSED BY THE ETA.
THE FORECAST SCENARIO THEN IS FOR THE SURFACE LOW TO CONTINUE TO
DEEPEN OVER SOUTHEAST COLORADO AND THEN MOVE EASTWARD ACROSS THE
FORECAST AREA TOMORROW MORNING WITH DRY SLOTTING TAKING PLACE BEHIND
IT. WILL ADJUST POPS ACCORDINGLY FOR THIS. BY TOMORROW AFTERNOON
WILL LOOK FOR THE COLDER NORTHERN BRANCH POLAR FRONT TO DRIVE SOUTH
BEHIND THE SURFACE LOW WITH INCREASING CHANCES FOR RAIN ALONG THE
FRONT OVERNIGHT. TEMPERATURES SHOULD BE COLD ENOUGH IN MY NORTHERN
ZONES TO CHANGE PHASE TO SNOW AFTER MIDNIGHT AND WINDS WILL BE
FAIRLY BREEZY FRIDAY NIGHT THROUGH SATURDAY IN THE COLD AIR
ADVECTION BEHIND THE FRONT. AT LEAST SOME CHANCE FOR PRECIPITATION
SHOULD LAST INTO SATURDAY MORNING BUT BY AFTERNOON SUBSIDENCE BEGINS
TO TAKE EFFECT ENDING THE PRECIPITATION. MAV TEMPERATURES LOOK
QUITE GOOD AND WILL GENERALLY USE THOUGH FRIDAY LOOKS TOO WARM.
WILL ADJUST POPS ACCORDING TO THE ABOVE REASONING.
DAYS 3-7...
THE OLR ANOMALIES INDICATE THAT WE ARE IN A DRY PHASE OF THE MJO
CURRENTLY. ALSO, THE AAM ANOMALIES INDICATE THAT THERE HAS BEEN A
PRETTY GOOD INCREASE IN THE GLOBAL ANGULAR MOMENTUM SINCE THE FIRST
OF FEBRUARY. THIS WOULD INDICATE MORE OF A PROGRESSIVE, ZONAL
PATTERN IN THE WESTERLIES WHICH THE MODELS DO INDICATE. THE MEDIUM
RANGE MODELS MAINLY DIFFER ON THE TIMING OF THE SHORTWAVES IN THE
FLOW, ESPECIALLY TOWARD THE MIDDLE OF NEXT WEEK. EXPECT A MILDER,
DRIER SETUP WITH THIS TYPE OF PATTERN. WILL THEREFORE KEEP FORECAST
DRY AND WILL GO WITH HIGHS MAINLY IN THE 50S FOR NEXT WEEK.
PRELIMINARY GUIDANCE FOR COORDINATION ONLY. OFFICIAL FORECASTS ARE
CONTAINED WITHIN THE DODGE CITY ZONE FORECAST.
DDC 42 52 32 37 / 60 0 0 0
GCK 38 51 32 38 / 60 0 0 0
EHA 44 54 35 44 / 60 0 0 0
LBL 46 56 34 43 / 60 0 0 0
HYS 35 45 30 31 / 60 60 60 30
P28 49 61 34 34 / 60 0 0 0
.DDC...NONE.
JOHNSON/LACY